Binary Organic Solar Cells Breaking 19% via Manipulating the Vertical Component Distribution.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Vertical component distribution significantly impacts organic solar cell (OSC) performance.
• This influence is primarily due to effects on exciton dissociation, charge-carrier transport, and recombination.

Purpose of the Study:

• To fabricate binary organic solar cells (OSCs) using sequential deposition (SD) of D18 and L8-BO materials.
• To optimize the spin-coating speeds for each layer to achieve high power conversion efficiency (PCE).
• To investigate the relationship between vertical component distribution and photovoltaic performance.

Main Methods:

• Fabrication of binary devices using a two-step sequential deposition (SD) process.
• Independent regulation of spin-coating speeds for each deposited layer.
• Fabrication of blend casting (BC) devices for comparison.
• Mechanism studies to analyze crystallinity, exciton splitting, energy loss, and charge transport.

Main Results:

• The optimal SD device achieved a record power conversion efficiency (PCE) of 19.05% for binary single-junction OSCs.
• The SD device's PCE was higher than the corresponding BC device (18.14%).
• The SD strategy demonstrated universality in enhancing photovoltaic performance across different nonfullerene acceptor systems.
• Mechanism studies revealed preferred vertical component distribution leads to high crystallinity, efficient exciton splitting, low energy loss, and balanced charge transport.

Conclusions:

• Sequential deposition (SD) with optimized vertical component distribution is a valuable approach for high-efficiency organic solar cells (OSCs).
• This method offers a significant improvement in power conversion efficiency (PCE) compared to blend casting.
• Understanding vertical component distribution is crucial for advancing OSC technology.